This invention relates to an electronic cylinder making method by which repetitively arranged same patterns are printed on a printed web.
Patterns printed, for example, on a structural member such as a decorative panel, floor material, wall paper, or printed fabric are mostly of an endless type in which the same patterns are continuously arranged in a given direction, or a multiple type in which the same patterns are repetitively arranged at a certain space, or a composite type in which the same patterns are impressed by a combination of both forms of arrangement. For example, the grain design is produced by the composite arrangement.
The known apparatus for electronically cylinder making the above-mentioned endless and/or multiple pattern includes HELIO-KLISHOGRAPH K-200 electronic cylinder making apparatus manufactured by Dr. Ing. R, Hell GmbH (hereinafter simply referred to as "the HELIO apparatus") set forth in the U.S. Pat. Nos. 4,057,838 and 4,013,831. Where an endless and a multiple pattern is processed by the HELIO apparatus, it is necessary to provide a special form of original which has a continuous pattern on the upper from lower sides, and on the right from left sides, and moreover portions of the pattern on the upper and lower sides are drawn with a same level of density, and portions of the patterns on the right and left sides are drawn with a same level of density. Generally, such original is photographically produced. The original is fitted to the peripheral surface of a reading cylinder. A pattern is engraved on a printing cylinder with a density signal obtained through a reading head. Where, in this case, the lengthwise portion of the original is engraved exactly on one circumference of the printing cylinder, then an endless pattern is processed. Where a pattern impressed on the original is repeatedly engraved in the axial direction of the printing cylinder, then a multiple pattern is processed.
However, considerable difficulties are encountered in preparing an original having a continuous pattern on the upper from lower sides and on the right from left sides, and moreover having the portions of the pattern on the upper and lower sides with a same level of density, and the portions of the pattern on the right and left sides with a same level of density. Even if a difference between the density with which, for example, the pattern appearing on the upper side is drawn and the density with which the pattern appearing on the lower side is drawn is so slight as can not be detected even by a densitometer, the density difference is distinctly indicated at the junction of the respective patterns appearing on an actual printed web. Consequently, failure of cylinder making, that is, failure to prepare an original is often discovered only after trial printing is undertaken from such original. Hitherto, therefore, it has been necessary to make a printing cylinder over again after correcting or remaking an original or a printing cylinder obtained therefrom. In any case, the above-mentioned work consumes a great deal of time and cost.